This application is a related application to U.S. Ser. No. 07/735 385, filed Jul. 24, 1991, now abandoned.
1. Field of the Invention
The present invention relates to a construction machine for use in digging and leveling the ground, particularly to an accessory detachable mechanism for detachably attaching an accessory to an arm of a construction machine.
2. Related Art
In construction machines for moving or digging in the ground, such as excavators, back hoes or the like, a conventional mechanism attached to an arm of the construction machine may be replaced by an accessory detachable mechanism according to the present invention. Excavators have been typically employed for earth work or construction work. A conventional excavator has an arrangement in which an accessory like a bucket or breaker is connected to the tip end of the arm. When the arm and the accessory are vertically swung by a hydraulic cylinder, earth and sand are dug out for forming holes or drains.
However, the excavator is used not only for digging holes or drains, but may be diverted to other projects which require different accessories. That is, instead of the bucket, another accessory may be connected to the arm so that specific earth work or construction work can be done. For example, the bucket may be selected to have the size adapted for a digging and trenching width, thereby enabling the excavator to work depending on hardness of earth and width of holes or drains. Alternatively, a breaker may be connected to the tip end of the arm or a grip may be employed for carrying out the loading or unloading of objects. A combination of various kinds of these accessories enables the excavator to adapt to various projects, thereby improving the applicability at the construction work site.
Changing accessories is troublesome and requires several people. Firstly, the bucket attached to the tip end of the arm is removed and another accessory for another project is manually connected to the arm. In this manual work, two pins connecting the arm and the bucket are removed to thereby detach the bucket from the arm. Successively, after another accessory is connected to the arm, connecting pins are inserted into the accessory and the arm.
A series of operations for attaching the accessory to or detaching the accessory from the excavator is carried out through tedious human effort. Several operators are involved in the attaching and detaching operations, which impedes the efficiency in the working site. Furthermore, since it takes time to align and replace pins and accessories, it was impossible to maximize replacement of the accessory at the working site.
According to the present invention, it is possible to quickly detach and attach accessories to the arm in order to reduce the numbers of the requisite operators and increase the efficiency of the work in the earth and constructions sites.
If one operator alone can attach the accessory to and detach the accessory from the arm, then the other operators required for replacing the accessory can be eliminated. Furthermore, in the connection between the arm and the accessory, if the connection between the arm and the accessory is made by pin connection using pins which insert shaft holes and not by a mere hooking connection, the connection is improved because less deformation of the mechanism will be achieved even if a great operating force is applied to the accessory and the arm.
Accordingly, in a first attempt to solve the accessory problem, the inventor proposed an accessory detachable mechanism including a pair of holding pawls which are provided at the tip end of the arm and capable of extending and contracting vertically (Japanese Patent Application No. 2-196763 and No. 2-250697). Similarly, a pawl is provided at the upper side of the tip end of the arm and a connecting pin, which can be stretchable rightward and leftward, is provided at the lower portion of the pawl (Japanese Patent Application No. 2-243203 and No. 2-243204). Furthermore, the inventor proposed a structure in which the arm has a horizontal groove which is open at the tip end thereof and a connecting rod fixed to the accessory is inserted inside the horizontal groove so as to be gripped by the horizontal groove after hooking the accessory by a pawl provided at the upper portion of the tip end of the arm (Japanese Patent Application No. 2-305558).
In these related arrangements as disclosed in copending U.S. Ser. No. 07/735 385, the arrangement is complex and the pawl is deformed if a great operating force is applied to the accessory. Furthermore, the arm and the accessory are frequently turnably operated and it is preferable that the arm and the accessory are connected by the pin connection.
It is desired to develop an accessory detachable mechanism for a construction machine capable of easily connecting the accessory to the arm, of simplifying the positioning of the pin holes through which the connecting pins are inserted and of connecting the accessory to the arm by pin connection. Furthermore, if desired, it is preferable that the accessory is connected to the arm by pin connection at two portions in front and rear portions of the accessory. The accessory is normally connected to the arm by the link mechanism in which both the accessory and the arm can be swingably connected to each other so that the angle between the accessory and the arm can be varied during the operation of the specific work object. Accordingly, if the operating force is applied to the accessory, this force is concentrated on the connecting portion whereby the connecting member is liable to deform if connected by only one connecting pin. Therefore, in the connecting mechanism between the accessory and the arm, it is preferable that the accessory and the arm are connected by pin connection at two or more portions thereof.